For the observer who is interested in watching the full range of fascinating behaviour
exhibited by dragonflies and damselflies. it is necessary to trace them to their breeding
sites. All but the most polluted aquatic sites are likely to support at least some species.
However, as we have seen, many others have quite specialised habitat requirements. In
order to observe all of the species currently breeding in the county, it would be necessary
to visit a number of quite different types of breeding site. The survey of Essex
dragonflies has provided considerable information about the range of habitats
colonised by the different species of dragonfly in our county, and reveals some
interesting relationships between human activity and dragonfly distribution.
Table 3:1 summarises the information we have about various types of habitat which
are used for breeding by the Essex species. Evidence of breeding may take the form of
nymphs or exuviae collected from the site or of copulating or ovipositing adults. In the
case of most damselflies. regular occurrence of good numbers at a particular site year
after year is sufficient evidence of a breeding population. The classification of habitat-
types is a rough-and-ready one. and corresponds mainly to the human use or origin of
sites of this type. Sites with very different origins or human uses can be ecologically very
similar, and some sites could readily fall under more than one category. Lakes, ponds
and flooded pits, for example, are overlapping categories, and also have very similar
ranges of breeding species. Some moving-water habitats - especially canals and slow
reaches of rivers - also have a similar range of breeding species, but the swifter rivers and
streams, and coastal ditches (some of them quite saline) tend to have a more specialised
and distinctive dragonfly fauna.
1. Still-Water Habitats
(a) Acidic Bog and Heathland Pools
Wet heaths and valley-bogs support more dragonfly species than any other type of
habitat. Unfortunately these sites are very vulnerable to destruction for building
development, afforestation, agricultural reclamation, or incompatible recreational
uses. Even where not directly threatened by human intervention, they are subject to
gradual invasion by scrub and woodland, and associated lowering of the water-table.
Such species as Ischnura pumilio (the Scarce Blue-tailed Damselfly), Orthetrum
coerulescens (the Keeled Skimmer), Ceriagrion tenellum (the Small Red Damselfly) and
Sympetrum danae (the Black Darter) are distinctive of these acidic breeding sites and so
their distribution in Britain as a whole is to a large extent limited by the amount of
remaining acid bog and wet heath.
Typical flora of acid bogs includes such species as Bog Asphodel. Sundew. Cotton-
grass. White Beak-sedge and Sphagnum moss. The heaths of the New Forest. Dorset
and Surrey still support considerable areas of this prime dragonfly habitat, but, as the
rarity or absence of the above plant species in Essex indicates, our county has only tiny,
fragmentary relics. The one dragonfly species characteristic of acidic pools which has
apparently survived in Essex is Sympetrum danae. This species eluded searches of small
remaining areas of suitable habitat in lipping forest, until one male was observed by A.
McGeeney in September 1987. However, it is too early to tell whether this indicates the
survival of a viable breeding population in the Forest.
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